Friday, December 7, 2012

Hurricane Impact Windows

Many methods of protecting a home against hurricanes exist. The current gold-standard in testing is the Miami-Dade County hurricane impact test. Be clear that products that meet or exceed this test are appropriate for all areas that may be impacted by hurricanes, tornadoes or other high wind situations. Remember, it is your life and your property. Essentially all of Florida, and all the coastal regions of the United States should prepare for possible wind speeds of 110 mph or greater.

The impact tests do not guarantee the windows will survive a hurricane, but they do test specific conditions that they should survive. Impact survivability certainly helps home survivability. If you can maintain the structural shell of your house or business, you are significantly more likely to save the structure. Once wind enters a building, it becomes much more likely that the structure will be significantly damaged. Therefore it becomes imperative to protect all the openings in your building.

THE IMPACT TEST, from the Miami Dade office of Code ComplianceThe Miami-Dade Building Code requires that every exterior opening - residential or commercial - be provided with protection against wind-borne debris caused by hurricanes. Such protection could either be shutters or impact-resistant products. There are two types of impact-resistant products: large-missile resistant and small- missile resistant.

Large-missile resistant A product is tested as large-missile resistant after it has been exposed to various impacts with a piece of lumber weighing approximately 9 pounds, measuring 2" x 4" x 6’ (no more than 8') in size, traveling at a speed of 50 feet per second (34 mph). Then the product must pass positive and negative wind loads for 9,000 cycles, with impact creating no hole larger than 1/16 x 5" in the interlayer of the glass. If you live in a building where doors and windows are located 30 feet or less above grade (e.g. above ground level) then the products must pass the large-missile test. If the doors and windows are more than 30 feet from the ground then they must be either large or small missile compliant.

Small-missile resistant A product is declared small-missile resistant after it has been exposed to various impacts with 10 ball bearings traveling at a speed of 80 feet per second (50 mph). The product is then subjected to wind loads for 9,000 cycles.